Salomon Hernandez-Vega, 38, was sentenced to six and a half years in prison after entering the U.S. illegally from Mexico back in 2013. The Federal Bureau of Prisons said that he was found unresponsive in his cell on Thursday at the Federal Correctional Institution Fairton in Cumberland County.

Hernandez-Vega had been housed at FCI Fairton since last November. The prison is a medium-security facility in Cumberland County with an adjacent minimum-security satellite camp. The two facilities house a total of nearly 1,200 male inmates.

Federal authorities are investigating the situation and the family has been notified.